1. Field of the Invention
The present invention relates to organic light emitting diode (“OLED”) devices. In particular, the present invention relates to a method and system for manufacturing OLED devices that degrades individual defective OLED pixels in the OLED device.
2. Description of Prior Art
An OLED device typically includes a stack of thin layers formed on a substrate. In the stack, a light-emitting layer of a luminescent organic solid, as well as adjacent semiconductor layers, is sandwiched between a cathode and an anode. The light-emitting layer may be selected from any of a multitude of fluorescent organic solids. Any of the layers, and particularly the light-emitting layer, may consist of multiple sub layers.
In a typical OLED, either the cathode or the anode is transparent. The films may be formed by evaporation, spin casting, other appropriate polymer film-forming techniques, or chemical self-assembly. Thicknesses typically range from a few monolayers to about 1 to 2,000 angstroms. Protection of OLED against oxygen and moisture can be achieved by encapsulation of the device. The encapsulation can be obtained by means of a single thin-film layer situated on the substrate, surrounding the OLED.
High resolution active matrix displays may include millions of pixels and sub-pixels that are individually addressed by the drive electronics. Each sub-pixel can have several semiconductor transistors and other IC components. Each OLED may correspond to a pixel or a sub-pixel, and these terms are used interchangeably herein.
OLED pixels have a threshold energizing signal at which point they turn on, and begin to emit light. As the energizing signal falls below the threshold level, a correctly operating OLED ceases to emit light. During the manufacture of an OLED device including an array of OLED pixels, disturbances or contamination may cause one or more OLED pixels to not operate properly. Due to processing issues or contamination, a few sub-pixels can remain on irrespective of the driving conditions. In particular, some OLED pixels may continue to emit light after the energizing signal has fallen below the threshold level. These defective sub-pixels, also called inoperative OLED pixels, may also be called stuck-on pixels or stuck-on OLED pixels.
In many applications the stuck-on sub-pixels are very undesirable, which may result in a zero tolerance for stuck-on sub-pixels. Out of millions of sub-pixels in a display it is typically very difficult to obtain a display with zero stuck-on pixels or sub-pixels. One or more stuck-on OLED pixels may compromise an entire array of OLED pixels, and conventionally may require that the entire array to be discarded.